1. Field of the Invention
The present invention relates to a fermentation cell in which a liquid is subjected to the action of microorganisms that are fixed on solid supports or that form freely moving cell masses, via agglomeration or flocculation, of a sufficiently large size to be retained by appropriately positioned grids or lattices. The solid supports either can have limited movement, as in the case of plastic bands fixed on a grid, or can be free moving, like granules or small balls of a material having a density greater than the density of the liquid. The solid supports can also take the form of balls of an appropriate gel, for example, alginates, acrylamides, etc. In the fermenter, the liquid circulates continuously from an inlet pipe positioned at one end of the fermenter toward an outlet pipe at the other end.
2. Related Art
The principles by which fermenters as described above operate are known. The typical fermenter of this type comprises, for example, a cylindrical cell having a primary axis that is vertical, the inlet pipe being disposed, as the case may be, either at the bottom or at the top of the cell, and the outlet pipe at the opposite end of the cell.
In these known fermenters, the microorganism supports, having a density greater than the liquid, are often carried upward because of gas absorbed, adsorbed or otherwise captured on the surface, or entrapped in the pores, of the supports, to form bridge structures. This grouping together of the supports results in a decrease in the support surface area that is readily accessible to the liquid in the fermenter, preventing the fermenter from functioning normally. The deleterious effects from the formation of bridge structures can be reduced if the cell is separated by means of horizontal lattices into several adjacent chambers. But even by this approach, the packing of the supports against the lattices may seriously disturb effective operation of the fermenter.